1. Field of the Invention
The present invention relates to a steering system for a vehicle, and more particularly to a four-wheel steering system for a vehicle in which the rear wheels are arranged to be turned in response to the turning of the front wheels when the steering wheel is turned.
2. Description of the Prior Art
Conventionally, a four-wheeled vehicle has a steering system which is adapted to steer only the front wheels. It has however been proposed for the purpose of improving the maneuverability of the vehicle to steer not only the front wheels but also the rear wheels. For example, the U.S. Pat. No. 4,467,885 discloses a four-wheel steering system for a vehicle in which a front wheel steering mechanism and a rear wheel steering mechanism are mechanically connected by way of a transmission shaft so that the rear wheels are turned in response to the turning of the front wheels.
Further, in the four-wheel steering system disclosed in Japanese Utility Model Public Disclosure No. 61-80169 filed on Oct. 31, 1984 and laid open to the public on May 28, 1986, a front wheel steering mechanism is mounted on a dash lower panel partitioning a cabin and an engine compartment, and is situated rearward of the engine and forward of the dash lower panel. A transmission shaft is supported rotatably and slidably in the axial direction by bearings fixed to a flower panel.
Further, the U.S. Pat. No. 3,183,991 discloses a four-wheel steering system for a vehicle in which a transmission shaft is jointed by means of a splined slipjoint.
It should be noted that the transmission shaft and the front wheel steering mechanism are moved or forced back quite easily if the engine is moved or forced back, for instance, due to an accident or crash resulting in a force being imposed on the vehicle in a longitudinal backward direction. An example would be a head-on collision. Under these circumstances, rearward movement of the engine would cause the engine to hit or strike against the front wheel steering mechanism, which, in turn, will drive the dash lower panel backwardly into the cabin where passengers are sitting. Known four-wheel steering systems do not make any provision to resist or withstand against such backward loads resulting from crashes. The desirability of preventing or resisting backward movement of the front wheel steering mechanism and the dash lower panel due to collisions will be appreciated.